1. Filed of the Invention
The present invention relates to an optical pickup apparatus for performing information recording or information reproduction to/from an optical type information recording medium with a plurality of light beams, and particularly to an optical pickup apparatus having a monitor mechanism for controlling each of the light beams to proper beam intensity.
2. Description of the Related Art
As an optical type information recording medium, for example, a CD (Compact Disk) and a DVD (Digital Video Disk or Digital Versatile Disk) have been known. Also, with respect to each of these CD and DVD, a write once optical disk capable of recording information once and a rewritable optical disk capable of erasing and rerecording information have been known.
As such various information recording media have been developed, the need for an optical pickup apparatus having compatibility capable of performing information recording or information reproduction without distinguishing these information recording media has been increasing in an information recordinging and reproducing apparatus.
By the way, in order to realize the optical pickup apparatus having compatibility, a plurality of light beams adapted for each of optical properties of the information recording media are required and further, it is necessary to control each of light beams so as to become proper beam intensity and apply the light beams to each of information recording mediua.
However, when an optical system comprises an inherent monitor mechanism for each of the plurality of light beams is constructed to achieve such problems, there are problems that scale or weight of the optical pickup apparatus becomes large.
The invention is implemented in view of such problems, and an object of the invention is to provide an optical pickup apparatus of which structure has the compatibility and can achieve, for example, miniaturization and weight reduction.
In order to achieve the object, an optical pickup apparatus according to the invention comprises: a plurality of light emission sources adapted to emit light beams having different wavelengths, respectively; an optical path joint unit adapted to join optical paths of the light beams to form common optical path; and a photodetection unit provided in the common optical path and adapted to detect the light beams, wherein each of light emission intensities of the light emission sources is controlled on a basis of a detection result detected by the photodetection unit.
According to the optical pickup apparatus with such a configuration of the invention, the optical path joint unit guides the light beams with the different wavelengths emitted from the light emission sources to the common optical path. Then, the light beams are detected by the photodetection unit provided in the common optical path and the light emission intensities of the light emission sources are controlled on the basis of the detection results. Therefore, the plurality of light beams can be detected by one photodetection unit and an optical pickup apparatus having compatibility capable of, for example, miniaturization and weight reduction is implemented.
Also, in order to achieve the object, there is provided the optical pickup apparatus according to the above described, wherein the number of the plurality of the light emission sources is two; the optical path joint unit comprises: a transparent medium having an first surface and a second surface, which are opposed to each other; and a semi-transmission film provided on the second surface; one of the light beams is incident on the first surface; and the other of the light beams is incident on the second surface.
According to the above described optical pickup apparatus with such a configuration of the invention, when one of the light beams is incident from a side of the first surface to the transparent medium, the one of the light beams is split into a first transmitted beam and a first reflected beam by the semi-transmission film and the first transmitted beam is emitted to an information recording medium and the first reflected beam is emitted to the photodetection unit through the transparent medium. Also, when the other of the light beams is incident from a side of the second surface, the other of light beams is split into a second reflected beam and a second transmitted beam by the semi-transmission film and the second reflected beam is emitted to the information recording medium and also the second transmitted beam is emitted to the photodetection unit through the transparent medium. That is, a part of the one of light beams is formed into the first reflected beam and a part of the other of light beams is formed into the second transmitted beam to be guided to the side of the common optical path and then the light beams (first reflected beam and the second reflected beam) are detected by the photodetection unit provided in the common optical path. Then, the light emission intensities of the light emission sources are controlled on a basis of the detection results, respectively. Therefore, each of the light beams can be detected by one photodetection unit to control each of light emission intensities of the light emission sources on a basis of each the detection result, and an optical pickup apparatus having compatibility capable of, for example, miniaturization and weight reduction is implemented.
Also, in order to achieve the object, an optical pickup apparatus of the invention is characterized in that the first surface and the second surface of the transparent medium are not parallel.
According to the above described optical pickup apparatus with such a configuration of the invention, the first surface and the second surface are set at angles in relation to the laser beams, respectively, so that multiple reflected light beam, which is a light beam reflected between the first and second surfaces repeatedly, does not reach the photodetection unit, that is, the multiple reflected light beam is emitted to a direction deviating from the common optical path. As a result of that, an influence of the multiple reflected light beam can be reduced to perform photodetection necessary to control the light emission intensities of the light emission sources, and the light emission intensities of the light emission sources are controlled with high accuracy.